Gasoline treatment



United States Patent GASOLINE TREATMENT Clarence A. Johnson, Princeton, and Seymour C. Schuman, Titusville, N. J., assignors to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey No Drawing. Application February 19, 1952, Serial No. 272,511

13 Claims. (Cl. 196-28) This invention relates to the treatment of hydrocarbon oils and is more particularly concerned with the treatment of a raw cracked gasoline fraction. The invention is concerned primarily with the treatment of raw cracked gasoline fractions to produce a finished gasoline of commercially acceptable sulfur content, storage stability and octane number.

At the present time it is desirable that commercially acceptable motor gasoline have a sulfur content of not greater than 0.3% by weight and preferably not greater than 0.1%, as measured in accordance with ASTM methods D129-49 and D90-47T. Specifications for commercial motor gasoline likewise require that it pass an existent gum test, in accordance with ASTM method D-381, in which the gasoline must show less than 5 mg. of gum per 100 ml. that commercial motor gasoline meet the storage stability requirements set forth in ASTM methods D910-48T or D52549. Finally, the demands of modern high compression engines make necessary the production of motor gasoline possessing a high octane rating, usually determined as clear research octane number in accordance with ASTM method D908-48T. Arithmetic averages in January 1952, for motor gasoline sold in U. S. cities indicate research octane ratings of 83.2 and 90.0 for regular and premium gasolines, respectively, with such gasolines containing an average of 1.35 and 1.75 cc./gal., respectively, of tetraethyl lead.

In modern petroleum refining practice, it is highly advantageous to convert part or all of the higher boiling fractions of the crude oil to materials boiling in the gasoline range. This is effected by processes which involve the cracking of the higher boiling hydrocarbons into hydrocarbons boiling in the gasoline range. However, in many cases, the gasoline fraction which is produced by cracking (hereinafter referred to as raw gasoline) requires further processing to provide a commercially acceptable product having a sulfur content, storage stability and octane number within the above specified limits. Various processes have been proposed for treating such raw gasoline fractions to bring them Within the desired specification limits, and some of these processes have been commercially used with varying effectiveness.

While sulfur compounds are found in varying amounts in petroleum crudes or fractions, the amount of such compounds often exceeds a value corresponding to 1.0% by weight of sulfur. When such a crude or crude fraction is cracked, the raw gasoline product thereby obtained may not meet the above limits with respect to sulfur content. Furthermore, the sulfur compounds in the raw gasoline often exist as thiophenes and compounds of similar cyclic structure. Such cracked raw gasolines are generally of moderate to high octane number, containing 10 to by volume of aromatic hydrocarbons and at least 20% by volume of olefins, and all known methods for removing cyclic sulfur compounds bring about the destruction or conversion of some of these unsaturated hydrocarbons. For example, when hydrogenation at In addition, it is highly desirable ice relatively high pressures and relatively low temperatures is employed, the olefins present in the cracked gasoline are completely hydrogenated to paraflins, i. e.

It is well known that such parafifins have clear research octane numbers which are as much as 40 octane numbers lower than the corresponding olefins from which they were formed. Thus, such treatment of a raw cracked gasoline fraction produces a finished gasoline which is generally of appreciably lower clear research octane number than the raw gasoline, and which is in all cases of lower clear research octane number than would have been obtained if said olefins had not been hydrogenated. Where the cracking operation produces a raw gasoline which satisfies octane number requirements without the addition of tetraethyl lead, e. g., above 83 clear research octane number, such utilization of conventional hydrogenation treatment to remove cyclic sulfur compounds results in a finished gasoline which is of considerably reduced clear octane number and which consequently requires significant quantities of anti-knock additives to achieve octane requirements. Thus, the principal problem which these cracked raw gasoline fractions of high octane number and high sulfur content present is the reduction of sulfur content to commercially acceptable limits without adverse effect upon the clear research octane number. Similarly, when such cracked raw gasoline fractions are relatively unstable, it is necessary to increase their stability to the desired extent without adverse efr'ect upon the other properties of the gasoline. These are problems which have not been solved in a satisfactory and efiicient manner by prior processes for treating raw gasoline.

A principal object of the present invention is to provide a process for treating raw gasoline fractions containing at least 20% by volume of olefins and more than 0.1% by weight of sulfur as thiophenic or other cyclic sulfur compounds, which process will eliminate a substantial portion of said sulfur compounds, while maintaining the major portion of said olefins.

It is a further important object to provide a process for treating said raw gasoline fractions, which will eliminate a substantial portion of said sulfur compounds, while increasing or at least maintaining the clear research octane ratings of said raw gasolines.

It is another object of the invention to provide a process of the character indicated which is also effective simultaneously to increase the stability of such raw gasoline fractions.

Still another object is to provide an improved cracked raw gasoline treating process which avoids the shortcomings of treating processes heretofore proposed.

It is a feature of the invention that cracked raw gasoline is treated at an elevated temperature and at a predetermined hydrogen partial pressure in the presence of a material having catalytic activity such that the objectionable cyclic sulfur bodies are converted into readily separable forms, and bodies which render the gasoline unstable are converted to more stable forms, without significantly decreasing the clear research octane number of the raw cracked gasoline, even when the octane number exceeds 80. in many cases, the process of this invention increases the octane number. Thus, the application of the process to raw gasolines of clear research octane number exceeding makes it possible to meet commercial 7 octane requirements without the addition of anti-knock agents.

In accordance with the invention, a cracked raw gasoline fraction containing over 0.1% by weight of sulfur as thiophenes and other cyclic compounds, and containing at least 20% by volume of olefins, is introduced,

together with hydrogen, into a treating zone maintained at a temperature of 900 to 1025 F., preferably at a temperature of about 925 to lO0 F, in contact with particulate material of the character hereinbelow described. The total pressure in the treating zone and the introduction of hydrogen and raw gasoline are controlled in known manner to provide a hydrogen partial pressure of 100 to 400 p. s. i. (pounds per square inch), preferably 125 to 350 p. s..i. The total pressure of the system may vary over a relatively wide range, but it is generally preferred to use a total pressure not exceeding about 800 p. s. i. g. (pounds per square inchgage).

The particulate contact material employed in the treating zone is an alumina of high surface area, viz., a surface area of atleast about 100 square meters per gram, preferably at least 125 square meters .per gram, as measured by low-temperature nitrogen adsorption. The alumina of high surface area employed in accordance with this invention comprises bauxite, activated alumina, and preparations of high. surface area derived from alumina gels.

Bauxite is a well known, native aluminum oxide in hydrated form, often containing iron. In commercial practice, bauxite is ground to the desired particle size and dehydrated by heat treatment, the bauxite then being said to be activated. This heat treatment is carried out at temperatures within a wide range, generally 600 to 1400 F. Activation of bauxite sometimes includes one or more additional processing steps like acid washing, and mechanical or magnetic separation of admixed minerals. While activated bauxite is a preferred contact material for the process of this invention, it is possible to charge ordinary bauxite into the reaction zone because at reaction temperatures of 900 to 1025 F. and at even higher regeneration temperatures the bauxite will undergo dehydration and, thus, become activated. Commercially available activated bauxite, such as is sold under trade names like Porocel and Cyclocel is very satisfactory for the purposes of this invention.

Activated alumina is a commercial product well known in the petroleum treating art and is described, for example, in Chemical Engineers Handbook (John H. Perry, ed.) third edition (1950), page 905. Alumina gels prepared by precipitation of aluminum hydroxide from an aqueous solution of a soluble salt such as the nitrate, followed by filtration, washing, drying and calcining of the precipitate by conventional procedures are also suitable contact materials for the process of this invention.

Activated bauxite is a preferred catalyst employed in the herein disclosed process and it has been found that its activity is such that it is most advantageously and efliciently employed with. hydrogen partial pressures in the lower portion of the above specified ranges, viz., hydrogen partial pressures below 300 p. s. i. Similarly, it has been found that when activated alumina is used, hydrogen partial pressures in the upper portion of the above specified ranges are most advantageously employed, viz., hydrogen partial pressures above 150 p. s. i.

While substantially pure hydrogen is advantageously used, a gas mixture containing hydrogen and inertgases, such as nitrogen or methane, may be employed with etficacy. In the latter case it is preferable to use a gas mixture having at least about by volume of hydrogen in order to avoid the necessity of passing excessively large amounts of gas through the'reaction zone to provide the desired hydrogen partial pressure of 100 to 400 p. s. i. and vin order to avoid the necessity of raising the total pressure of the system to a high value.

The term gasoline fraction as herein used has its conventional meaning, viz., a hydrocarbon fraction boiling within the temperature range of 90 to 400 F., although it will be apparent that the treating process of this invention is applicable to hydrocarbon fractions in.which material boiling within the gasoline range comprisesthe predominant portion of the fraction.

Cracked raw gasoline fractions from various sources are advantageously treated in accordance with the process of the invention but the improved process is of particular value, as already mentioned, in reducing the sulfur content of cracked raw gasoline fractions of relatively high octane number, e. g., clear research octane numbers of at least about 80, and more particularly between and 90, containing substantial quantities of mono-olefins, such as gasoline fractions produced by the process described and claimed in the copending application of Percival C. Keith, Serial No. 139,758, filed January 20, 1950, now U. S. Patent No. 2,606,862. As previously mentioned, the present process is effective to remove even large proportions of sulfur bodies, including thiophenes and similar cyclic compounds, without any appreciable adverse effect upon the high octane number of the raw gasoline. In some cases the octane number is essentially unaffected, i. e., it is not changed by more than one or two units, whereas in other cases it is even increased by a substantial extent.

In the process described in the above-mentioned Keith application, a crude hydrocarbon oil, particularly a heavy residual product, is cracked at a temperature of 800 to 1050 F. and at a total pressure of 200 to 800 p. s. i. g. in the presence of a particulate contact material and the regeneration product gases produced by treating spent contact material contaminated with carbonaceous material at a temperature of about 1600 to 2500 F. with steam and oxygen of at least by volume purity. The hydrocarbon effluent from that process is fractionated to yield a cracked raw gasoline which may suitably be treated by the process of this invention.

The invention is, however, not limited to cracked raw gasoline fractions produced in any particular manner but is applicable to any cracked raw gasoline having at least 20% by volume of olefins, and thus a clear research octane number greater than that of a virgin naphtha, e. g., above about 40. The present process is of particular effectiveness, however, on those cracked raw gasoline fractions having an exceptionally high olefin content, c. g., of the order of 30% by volume higher, and high clear research octane numbers of the order of 80 to 90.

A typical raw gasoline produced by the process of the above-mentioned Keith application has a relatively high octane number, e. g., a clear research octane number of about 90, and contains a high proportion of olefins. Such a raw gasoline generally has, however, a substantial amount of diolefins which tend to render the gasoline unstable as by depositing gums on standing, and when the gasoline has been derived from a crude oil of very high sulfur content, the raw gasoline generally has a substantial quantity of cyclic sulfur compounds such as thiophenes. For example, a Boscan (Venezuelan) crude is characterized by a very high sulfur content of the order of 5% by Weight and, whenlcracked, the resulting raw gasoline will contain about 1.5% by weight or more of sulfur. Thus, although the sulfur content has been reduced, it has not been sufiiciently reduced to meet commercial motor gasoline specifications. Cracked raw gasoline fractions to which the present process is of particular application, such as gasoline produced in accordance with the above-mentioned Keith procedure, will generally have the following approximate composition (per cent by volume) Without tying the invention to any particular theory of operation, the process appears to involve the follow- "ing types of reactions which take place more or less simultaneously. Thiophenes and related cyclic sulfur compounds are converted .to normally gaseous sulfur compounds like hydrogen sulfide, and diolefins are converted to mono-olefins with the formation of some polymeric material. At the same time, aromatic hydrocarbons are not affected and only mild hydrogenation of mono-olefins takes place so that the excellent antiknock properties of the raw gasoline are not impaired. In addition, dehydrogenation of naphthenes is facilitated by the conditions employed, resulting in the formation of additional quantities of aromatic compounds of excellent anti-knock characteristics.

The raw gasoline treating process is suitably carried out in conventional gasoline treating apparatus wherein, in accordance with the invention, the raw gasoline is introduced into a reaction zone in contact with the catalyst.

The apparatus shown in the above-mentioned Keith application may be employed, but preferably the process is carried out in a fluidized bed such as is used commercially in the catalytic cracking of hydrocarbon oils, the hydrogen or hydrogen-containing gas being advantageously employed as the fiuidizing medium. The contact material is continuously or intermittently withdrawn from the treating zone and regenerated in any convenient manner, as by treating it at elevated temperature with oxygen or air and, if desired, other gaseous materials such as steam.

The particular apparatus used for the process and the particular method of regenerating the catalyst form no part of the present invention and any convenient apparatus and method of catalyst regeneration may be employed. In regenerating the catalyst care must be taken, however, in accordance With commercial regeneration techniques, to avoid the use of temperatures which destroy or adversely affect the catalyst. In the regeneration of the catalyst of the present process, temperatures in excess of 1400" F. are generally to be avoided.

In order to facilitate the maintenance of the desired temperature in the reaction zone, the raw cracked gasoline to be treated is advantageously preheated to a temperature of 400 to 800 F., preferably about 500 to 7.00 F., before being fed 'into the reaction zone. At such temperatures the gasoline is at least partially vaporized. The hydrogen or hydrogen-containing gas may also be preheated to about the same temperature as the gasoline.

Treatment of the cracked raw gasoline in the reaction zone under the specified conditions is carried out to an extent sufficient to reduce the sulfur content of the raw gasoline and to improve its stability to the desired degree. by employing a raw gasoline feed rate in the range of 0.5 to 5, preferably 0.5 to 1.5, volumes of liquid per hour per volume of catalyst, while employing a hydrogen flow rate of 500 to 2500 standard cubic feet (calculated as pure hydrogen) per barrel of raw gasoline fed.

The effluent from the treating zone will contain vapors of the hydrocarbons within the gasoline range admixed With a small amount of higher boiling hydrocarbons formed by polymerization and/or condensation in the reaction zone, and with more volatile compounds including readily removable sulfur compounds formed by the breakdown of thiophenes and like refractory sulfur compounds in the reaction zone. The efiluent is fractionally distilled to separate the desired gasoline fraction from the other constituents.

The finished gasoline fraction thus produced is of low sulfur content, high stability and high octane number and meets the specifications for commercial motor gasoline notwithstanding the presence of a substantial quantity of sulfur compounds and diolefins originally in the cracked raw gasoline. The sulfur content of the finished gasoline can be reduced to below 0.1% by Weight by the present process, as well as below the 0.3% by weight level presently accepted for marketable motor gasoline.

For a further understanding of the invention, reference is made to the following specific examples which are Advantageously, the desired reaction is insured treating a raw gasoline derived from Boscan crude.

intended as illustrative of the process without, however, being intended as limitative thereof.

In the following examples the cracked raw gasoline which is treated was obtained from heavy hydrocarbon oils which were subjected to cracking in accordance with the aforesaid Keith process at a temperature of about 900 F. in the presence of the regeneration gases resulting from the decomposition of the carbonaceous residue on the particulate carrier with steam and oxygen of by volume purity at a temperature of about 1700 F. The effluent from the cracking operation was condensed and fractionally distilled to separate the raw gasoline fraction.

This raw gasoline fraction is heated, for example, by passing through the coils of a tube still to a temperature of about 700 F. The gasoline is then discharged into a reaction zone containing fluidized particles of alumina of high surface area. The gaseous treating atmosphere is provided and the fluidization of the catalyst particles is effected simultaneously by introducing a stream of hydrogen into the bottom of the reaction zone. A portion of the fluidized catalyst is continuously removed I from the reaction zone and passed to a regenerator, and

a corresponding amount of regenerated catalyst, with or without pretreatment with hydrogen, is continuously returned to the reaction zone. The heated raw gasoline is introduced into the reaction zone at the desired space velocity and the desired reaction temperature is obtained by controlling the preheat of the reactant feeds. The hydrogen flow and total pressure are controlled to provide the desired hydrogen partial pressure.

Table I summarizes the results of Examples 1 to 6. Sulfur as thiophcnes, reported herein, Was determined by the Bureau of Mines procedure (R. I. 3591, December 1941). The olefin content of the raw cracked gasolines was determined by chromatographic adsorption analysis. However, the olefin content of the finished gasolines, from which thiophenes and other interferents have been substantially removed, was determined conventionally by the A. S. T. M. bromine number procedure. Other analyses were obtained utilizing conventional A. S. T. M.

.procedures, as indicated.

Example 1 illustrates the process of the invention on a raw gasoline derived by cracking Boscan (Venezuela) crude, this raw gasoline containing 1.65% by weight of total sulfur and indicating a clear research octane number of 87. The finished gasoline, obtained as described above.

using bauxite (Cyclocel) as catalyst, contains only 0.29% by weight of sulfur, and the clear research octane number has been increased to 89.4.

Example 2 illustrates the use of somewhat different operating conditions on a similar raw gasoline. In this case, the finished gasoline contains only 0.18% by weight of sulfur, with a small loss in clear research octane number to 85.7.

Example 3 illustrates the process of the invention on a raw gasoline derived by cracking West Texas-New Mexico residuum and employing a hydrogen-containing gas comprising 50 mol per cent hydrogen admixed with inert gas. In this case, where the required amount of desulfurization is relatively small, the lower limit or" temperature Within the prescribed range can be employed with eflicacy.

Example 4 illustrates the use of activated alumina for In this case, the finished gasoline contains 0.20% by weight of sulfur, and the clear research octane number has been increased from 87 to 90.5, meeting commercial requirements for premium gasoline Without utilization of anti-knock additives.

Example 5 illustrates the importance of maintaining temperature within the prescribed limits. In this case, with operating conditions approximately the same as those of Example 4 except for a reduction in temperature from 970 to 912 F., the finished gasoline contains 0.37% by weight of sulfur. Such gasoline can be utilized by blending with other gasoline of lower sulfur content. However, further appreciable reduction in treating temperature would produce a finished gasoline of unusable quality.

Example 6 demonstrates the effect of an increase in hydrogen partial pressure from 182 to 325 p. s. i. while employing other operating conditions substantially the same as in Example 5. Although the finished gasoline produced in Example 6 contains 0.21% by weight of sulfur, the clear research octane number is reduced to 85.2. Further increase in hydrogen partial pressure to a point outside of the prescribed process limits will produce still more marked reduction in clear research octane number, necessitating the use of anti-knock additives to meet motor fuel requirements.

The finished gasolines produced in Examples 1 to 6 have a gum content and a storage stability which are considerably superior to the corresponding properties of the tion resulting in a net consumption of hydrogen, passing said hydrocarbon fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 400 p. s. i., and recovering from the resulting reaction effluent a highly olefinic hydrocarbon fraction containing less than 0.3% by weight of sulfur and a major portion of said olefins and having a high octane number.

2. A method of desulfurizing a highly olefinic hydrocarbon fraction, which comprises bringing hydrogen and a hydrocarbon fraction containing more than 0.1% by weight of sulfur in the form of cyclic sulfur compounds and more than 30% by volume of olefins imparting to said hydrocarbon fraction a high octane number into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 925 to l000 F.,

raw gasolines, and which meet commercial requirements. the contact of said hydrogen and said hydrocarbon frac- These finished gasolines contain a major portion of the tion resulting in a net consumption of hydrogen, passing olefins originally present in the raw gasoline, and meet said hydrocarbon fraction through the reaction zone at motor octane requirements without the use of anti-knock a space velocity in the range of about 0.5 to 5.0 liquid additives. volumes per hour per volume of said alumina, maintain- An additional test was conducted using substantially 2} ing the partial pressure of hydrogen in said reaction zone the same conditions of Example 2, except that instead in the range of 100 to 400 p. s. i., and recovering from of hydrogen, nitrogen was employed. In this case, the the resulting reaction efiluent a highly olefinic hydrocarsulfur content of the finished gasoline was 1.17% by bon fraction containing substantially less than 0.1% by weight, indicating essentially no removal of the thiophenic weight of sulfur and a major portion of said olefins and sulfur present in the raw gasoline. having a high octane number.

In tests similar to those illustrated above, it has been 3. A method of desulfurizing a highly olefinic gasoobserved that, in addition to removal of sulfur from raw line fraction, which comprises bringing hydrogen and a cracked gasoline, the process of this invention is effective gasoline fraction containing more than 1% by weight of in removal of oxygen and nitrogen compounds which sulfur in the form of cyclic sulfur compounds and more may likewise be present in such raw gasolines. than 30% by volume of olefins and having a clear re- In view of the various modifications of the invention Search Octane num r of at least about 80 into contact which will occur to those skilled in the art upon considera- Wlth an alumlna of g Surface ar a and free of added tion of the foregoing disclosure without departing from ca alysts and promoters in a reaction zone maintained t the spirit or scope thereof, only such limitations should a temperature in the range of 925 to 1000 F., the conbe imposed as are indicated by the appended claims. tact of said hydrogen and said gasoline fraction resulting Table I Example Number 1 2 3 4 5 6 Catalyst CyeloccL. CycloceL. Cycloeel Activated Alu- Activated Alu- Activated Alumma. Raw Gasoline (400 F. E. P.) Boseannn Boscan W. T.New Mex." Boscan.

Total stnrur, Wt. Percent; (ASTM-D129-49). 0.44 1 1.65.

Sulfur as Thiophcnes, Wt. Percent; 1 1.2.

Octane Number, OFRR Clear (ASTM- 87.

D908-48T). Copper Dish Gum, mgJlOO ml. (ASTM- 150.

Olefin Content, Vol. Percent 45. Operating Conditions:

Temperature, F 926.

Pressure, 1). s. i. g... 400.

Space Velocity, V./lil'./V 0.5.

Hs drcgcn Purity, mol Percent 100 Hydrogen Partial Pressure, p. s. 325.

Yields, Percent of Raw Gasoline Char Finished. Gasoline (C -400 F. E. P.), V. 84.2 89.3.

Percent.

Total Liquid (04+), V. Percent: 83.5 00.0 94.1. Finished Gasoline Quality:

Total Sulfur, Wt. Percent (ASTM-D129-49). 0.20 0.18 0.21

Octane Number, CFRR Clear (ASIM- 8t).4 85.7 85.2

BromineNumbcr,cg./gm.(ASlM-D875-46). 34 s. 41 59.

Olefin Content, Vol. Percent 24... 40.

Copper Dish Gum, mg./100 ml. (ASTM- 28.

Dale-4ST). Existent Gum,rng./100ml.(ASTM-D38t-49). 5 5.

in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of to 400 p. s. i., and recovering from the resulting reaction effluent a highly olefinic gasoline fraction containing less than 0.3% by weight of sulfur and a major portion of said olefins and having a clear research octane number of at least about 80.

4. A method according to claim 3 wherein the alumina of high surface area is activated bauxite and the hydrogen partial pressure is in the range of 125 to 300 p. s. i.

5. A method of desulfurizing a highly olefinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing more than 0.3% by weight of sulfur in the form of cyclic sulfur compounds and more than 30% by volume of olefins and having a clear research octane number of at least about 80 into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 925 to 1000 F., the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 400 p. s. i., and recovering from the resulting reaction eflluent a highly olefinic gasoline fraction containing less than 0.3% by weight of sulfur and a major portion of said olefins and having a clear research octane number of at least about 90.

6. A method of desulfurizing a highly olefinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing more than 0.1% by Weight of sulfur in the form of cyclic sulfur compounds and more than 20% by volume of olefins imparting to said gasoline fraction a high octane number into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 900 to 1025 F., the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 400 p. s. i., and recovering from the resulting reaction eflluent a highly olefinic gasoline fraction containing substantially less than 0.1% by weight of sulfur and a major portion of said olefins and having a high octane number.

7. A method of desulfurizing a highly olefinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing more than 0.1% by weight of sulfur in the form of cyclic sulfur compounds and more than 20% by volume of olefins and having a clear research octane number of at least about 80 into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 925 to 1000 F., the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 125 to 350 p. s. i., and recovering from the resulting reaction etfiuent a highly olefinic gasoline fraction containing substantially less than 0.1% by weight of sulfur and a major portion of said olefins and having a clear research octane number of at least about 80.

8. A method according to claim 7 wherein the gasoline fraction passes through the reaction zone at a space velocity of 0.5 to 1.5 liquid volumes per hour per volume of said alumina.

9. A method of desulf'urizing a highly oleiinic gasoline fraction, which comprises bringing hydrogen and a gasoline fraction containing more than 0.1 by weight of sulfur in the form of cyclic sulfur compounds and more than 30% by volume of olefins and having a clear research octane number of at least about into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 925 to 1000 F., the contact of said hydrogen and said gasoline fraction resulting in a net consumption of hydrogen, passing said gasoline fraction through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of to 400 p. s. i., and recovering from the resulting reaction effluent a highly olefinic gasoline fraction containing substantially less than 0.1% by weight of sulfur and a major portion of said olefins and having a clear research octane number of at least about 90.

10. A method according to claim 9 wherein the alumina of high surface area is activated bauxite and the gasoline fraction passes through the reaction zone at a space velocity of 0.5 to 1.5 liquid volumes per hour per volume of said alumina.

11. A method of desulfurizing a highly olefinic gasoline, which comprises bringing hydrogen and a raw gasoline containing an appreciable quantity of troublesome foreign matter of the class of cyclic sulfur compounds and gum-forming bodies and containing more than 20% by volume of olefins, said raw gasoline having a clear research octane number of at least about 80, into contact with an alumina of high surface area and free of added catalysts and promoters in a reaction zone maintained at a temperature in the range of 925 to 1000 F., the contact of said hydrogen and said raw gasoline resulting in a net consumption of hydrogen, passing said raw gasoline through the reaction zone at a space velocity in the range of about 0.5 to 5.0 liquid volumes per hour per volume of said alumina, maintaining the partial pressure of hydrogen in said reaction zone in the range of 100 to 400 p. s. i., and recovering from the resulting reaction efiluent a highly olefinic finished gasoline substantially free of troublesome foreign matter and containing at least 20% by volume of said olefins and having a clear research octane number over 80.

12. A. method according to claim 11 wherein the alumina of high surface area is activated bauxite and the hydrogen partial pressure is in the range of to 300 p. s. 1.

13. A method according to claim 11 wherein the alumina of high surface area is activated alumina and the hydrogen partial pressure is in the range of to 350 p. s. 1.

References Cited in the file of this patent UNITED STATES PATENTS 1,955,297 Jennings Apr. 17, 1934 2,315,506 Banner et al Apr. 6, 1943 2,345,575 Burk et al Apr. 4, 1944 2,371,298 Hudson et al Mar. 13, 1945 2,419,029 Oberfell Apr. 15, 1947 2,498,559 Layng et al Feb. 21, 1950 2,500,146 Fleck et a1 Mar. 14, 1950 2,516,877 Home et a1 Aug. 1, 1950 

1. A METHOD OF DESULFURIZINGG A HIGHLY OLEFINIC HYDROCARBON FRACTION, WHICH COMPRISES BRINGING HYDROGEN AND A HYDROCARBON FRACTION CONTAINING MORE THAN 1% BY WEIGHT OF SULFUR IN THE FORM OF CYCLIC SULFUR COMPOUNDS AND MORE THAN 20% BY VOLUME OF OLEFINS IMPARTING TO SAID HYDROCARBON FRACTION A HIGH OCTANE NUMBER INTO CONTACT WITH AN ALUMINA OF HIGH SURFACE AREA AND FREE OF ADDED CATALYSTS AND PROMOTERS IN A REACTION ZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF 900 TO 1025* F., THE CONTACT OF SAID HYDROGEN AND SAID HYDROCARBON FRACTION RESULTING IN A NET CONSUMPTION OF HYDROGEN, PASSING SAID HYDROCARBON FRACTION THROUGH THE REACTION ZONE AT A SPACE VELOCITY IN THE RANGE OF ABOUT 0.5 TO 5.0 LIQUID VOLUMES PER HOUR PER VOLUME OF SAID ALUMINA, MAINTAINING THE PARTIAL PRESSURE OF HYDROGEN IN SAID REACTION ZONE IN THE RANGE OF 100 TO 400 P.S.I., AND RECOVERINGG FROM THE RESULTING REACTION EFFLUENT A HIGH OLEFINIC HYDROCARBON FRACTTION CONTAINING LESS THAN 0.3% BY WEIGHT OF SULFUR AND A MAJOR PORTION OF SAID OLEFINS AND HAVING A HIGH OCTANE NUMBER. 